Buttress type steel dam for collecting debris



p 0, 6 SHIGEFUMIITANAKA ETAL 3,469,403

BUTTRESS. TYPE STEEL DAM FOR COLLECTING DEBRIS Filed Feb. 9, 1967 3 Sheets-Sheet l FIG. I

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A '3 INVENTORSY Shigefumi Tanaka J i re Tosiaki Mafumofo MM M Ishikawa Sept. 30, 1969 SHIGEFUMI TANAKA ETAL 3,469,403

BUTTRESS TYPE STEEL DAM FOR COLLECTING DEBRIS Filed Feb. 9, 1967 3 Sheets-Sheet r:

FIG.3

Bv v 14 H 1 1O 9 j INVENTORS 3 Shigefumi Tanaka J iro I shikawa Tosiaki Malumolo mwmig w l 30, 1969 I SHIGEFUMI TANAKA ETAL 3,469,403

BUTTRESS TYPE STEEL DAM FOR COLLECTING DEBRIS Filed Feb. 9. 1967 3 Sheets-Sheet 5 FIG.5

INVENTORS Shigefumi Tanaka J iro I shikawa BY Tosiaki Mafumo'o United States Patent US. Cl. 61-3 4 Claims ABSTRACT OF THE DISCLOSURE A buttress type steel darn as a debris barrier having great durability and stability against water pressure and debris pressure acting on the surface of dam body and particularly suitable for a dam to be constructed on the bed of a river having swift stream in mountainous region, which can be constructed very rapidly and economically by assembling on a spot steel materials ready made in a factory.

This invention relates to a steel dam to be established on a river bed for preventing debris of river bed, that is, earth, sands and gravels on river bed, particularly on river bed of the mountainous region, where the river stream is very swift, from being swept away by the stream.

In the rivers of swift stream in the mountainous region the river beds are often corroded on account of a lot of debris being washed away by the swift stream, and a breakdown of embarkment and landslip arise therefrom. Particularly, in the flood time collapsed sands and gravels intercept the stream of river and cause it to overflow in the down stream, thereby often causing serious damages. Therefore, it is a grave problem to prevent debris of river bed from being swept away by the stream.

Heretofore, as measures of preventing debris of river bed from being swept away by stream, there have been employed dams of various types, for instance, wet masonry dam (a dam which is prepared by jointing stones with mortar), boulder concrete dam (a dam which is prepared by boulders and concrete), concrete darn, dam using concrete pipes of large diameter, wire cylinder darn or mortargrouting dam. However, all these dams are of water-intercepting wall type, and they are all a debris barrier and at the same time a reservoir dam. Consequently, in designing the dams of this type water pressure, including that at the flood time, must be taken into consideration. Moreover, the construction of these dams takes much time and is accompanied by difliculties, because the place of construction is mountainous region. Thus, the conventional dams have drawbacks in the working and economic aspects.

This invention is to provide a darn the structure of which is made water-passing-through type from a view point of discarding the function as a reservoir which is unnecessary for a debris barrier and which may be con structed as desired in a simple way and in a very short period of time by previously preparing in a factory steel materials which are to be assembled to a dam according to the state of a river, in which the dam is to be constructed, and transporting them from the factory to the construction site.

Therefore, the primary object of this invention is to provide a steel dam as a debris barrier which is of a waterpassing-through type.

Still another object of this invention is to provide a steel dam as a debris barrier which may be assembled easily and simply at a construction site.

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Still another object of this invention is to provide a steel dam as a debris barrier which may be constructed rapidly and yet less steel materials to a stable construction of a much greater strength than conventional dams.

FIG. 1 is a vertically sectional side view of a debris barrier of this invention (section on the line A-A in FIG. 2). FIG. 2 is a front view of the debris barrier shown in FIG. 1 as seen from the upper stream side. FIG. 3 is a vertically sectional side view of another sample of the debris barrier of this invention (section on the line BB in FIG. 4). FIG. 4 is a front view of the debris barrier shown in FIG. 3 as seen from the upper stream side. FIG. 5 is a sketched side view of an example of the debris barrier of this invention established on an inclined river bed. FIGS. 6 and 7 are the sketches of the debris barrier prepared for the sake of the explanation thereof.

The structure of the debris barrier of this invention will be explained in detail in the following with reference to the attached drawings.

According to this invention a barrier body 1 made of steel, through which water stream is passable, is established in such an inclined state that the upper part of the barrier body is positioned more to the downstream side of the river than the lower part thereof, and the lower part thereof is fixed to a concrete foundation 3 established on a river bed 2. Then, inclined staying members 4 made of steel are connected at their upper end to the barrier body on its back side (down stream side) at a point somewhat higher than the middle of the longitudinal length of the barrier body 1, and at their lower end to a concrete foundation 5 established on the river bed 2.

The barrier body 1 is constructed as follows: Several longitudinal rods 6 made of shape steel, for instance, H-formed steel, are erected in parallel on the foundation 3 with a certain distance between each rod respectively in such an inclined state that the upper part thereof is positioned more to the down stream side, while the lower part thereof is more to the upper stream side. In front of the said longitudinal rods a number of lateral rods 7 made of angle steel are fixed screenwise to the former by welding or bolting, that is, in such a way that gaps 8 of small distance for water passage are formed between each rod (ref. to FIGS. 1 and 2).

This invention is not limited to the above mentioned example. The barrier body 1 may also be so constructed that a framework is first prepared by fixing several lateral rods 9 made of shape steel, for instance, channel steel, to several longitudinal rods 6 made of H-formed steel by welding or bolting at certain intervals, and then a number of metal plates 11 providing with holes 10 for water passage are fitted so said framework by welding or bolting (ref. to FIGS. 3 and 4).

In the drawings, 12 indicates bolts for fixing washers 13 fastened to the upper part of each..staying member 4 to a flange of each longitudinal rod 6 of the barrier body 1, and 14 a concaved upper edge of the barrier body formed at the central part thereof. When a flow of river is so increased to overflow the barrier body, it overflows mainly this concave part of the barrier body. 15 is a reinforcement made of shape steel, for instance, H- formed steel, which is fastened by bolts between the longitudinal rod 6 and the staying member 4. This reinforcement is effective for the barrier body of a large type. Therefore, this is not an indispensable constitutent of the barrier construction of this invention.

FIGS. 1 to 4 show the barrier construction to be applied to the case of the river-bed surface being in a substantially horizontal state. However, in th case the river-bed surface being of such a steep gradient as it can scarcely be levelled or can not be adjusted by the founda tions 3 and 5 to the level, the construction should be modified as shown in FIG. 5. In such a case, it is necessary to make the inclination of the barrier 1 to the upper stream side gentle, thereby to make the resistance element to the water load large, or to make the rooting of the foundation sufficiently large.

As already mentioned, all members constituting the barrier construction of this invention are previously calculated, designed and manufactured in a workshop. For steel materials to be used in the present invention readymade shape steels including H-formed steel, channel steel, angle steel and any other kinds may be applied. The premanufactured members are then transported to a field and built-up to barrier construction on the spot. At this time, the foundations 3 and 5 are also established in advance on the river-bed, where the dam is to be established. The depth of rooting of the foundations in the ground is controlled according to th conditions (hard or soft) of the ground of the river-bed. Then, the longitudinal rods 6 and the staying members 4 are connected with each other and they are fixed successively to the foundations 3 and 5. It is advisable to temporarily fasten the longitudinal rods with the lateral rods of proper number so that the distances between longitudinal rods may be kept to be parallel. When fixing the lower ends of the longitudinal rods 6 and of the staying members 4 to the foundations 3 and 5, it is preferable to further embed the lower ends of the longitudinal rods and the staying members in concrete on the foundations 3 and 5. After a number of the longitudinal rods and the staying members are erected at the fixed positions on the foundations, the lateral rods are fixed to the longiutdinal rods with a certain distance respectively by welding or bolting to constitute the barrier body 1. As already mentioned, it is also possible to construct the barrier body by fixing the metal plates 10 having water passage holes 11 there in to the framework consisting of the longitudinal and lateral rods. As occasion demands, truss members 15 and 15' may also be applied. It is needless to say that steel materials of proper strength should be selected in accordance with the real circumstances of constructing the debris barrier. Thus, the buttress type debris barrier of the present invention may obtain a very stable construction, because the barrier body is established in an inclined state and is of a water-passable structure.

A buttress type dam itself is well known. However, it has theretofore been applied to a dam for use in a reservoir only. In such a case, as there is little possibility of debris being accumulated on the surface of the dam body with the lapse of time, the design of the buttress type dam for use in a reservoir has for its object mainly a load composed of a vertical component and a horizontal component of water weight. And the vertical component of water weight has been particularly utilized for the purpose of securing the stability of the darn body, thereby to reduce an amount of concrete to be used.

In the case of applying the buttress type dam for a novel purpose as is proposed by the present invention, that is, for use in a debris barrier the situation is different. In this case an accumulation of debris coming from the upper stream on the surface of the dam body proceeds with the lapse of time, which brings about an effect of keeping down the dam body. Consequently, the proper characteristic of the buttress type dam which can not be expected from dams of other types, that is, that of securing the basic stability of the dam against overturning or slipping of the dam body, is displayed more and more as the accumulation of debris proceeds. In designing the buttress type dam as a debris barrier as is proposed by the present invention, therefore, a shift of load from water weight to debris weight can be taken into consideration in the direction of displaying the proper characteristic of the buttress type dam.

Further, when the buttress type dam is constructed for use in a reservoir the site of possibly slow gradient is to be selected for the purpose of enlarging an amount of water to be reserved. On the contrary, the buttress type dam as a debris barrier of the present invention may be constructed on a steep site in the river of swift stream.

On the other hand, as a conventional debris barrier there has usually been constructed a concrete waterintercepting darn. In this case debris coming from the upper stream will be accumulated on the darn body with the lapse of time and will be tight by means of tractive force. In this state, as a load acting on the dam body debris pressur will be greater than water pressure. However, during the period immediately after the completion of the dam, when there is still no accumulation of debris, a stream containing debris will entirely be dammed up, if a fiood is caused in such a state. Therefore, a dangerous state must be expected if a flood is caused immediately after the completion of the dam, that is, during the period when there is still no accumulation of debris coming from the upper stream on the surface of the dam body.

On the other hand, in the debris barrier of the present invention, which is of water passable construction, the load acting on the barrier body is largely reduced in the period when there is still no accumulation of debris, because the stream will pass through the barrier body to the down stream side. Therefore, in the safety design of the debris barrier of the present invention the state of debris having been accumulated should be more taken into consideration than the state before the accumulation thereof.

As the accumulation of debris on the surface of the barrier body effects favorably in increasing the stability of the barrier body against overturning or slipping thereof, the gradient of the barrier body on the upper stream side, or in other words, an angle of the barrier body to the river bed may be made larger than the case of a conventional debris barrier of Water-intercepting type, resulting in following advantages: With a steeper gradient of the barrier body surface the span of the barrier body may be shortened, and as result thereof the maximum bending moment may be made smaller, and thereby sections of member materials to be desired may be reduced. Or the length of member materials may be shortened. Or depending on the conditions of the foundations, an amount of concrete used for the foundations may be economized, leaving the gradient of the barrier body as it is.

The angle (6) of the barrier body varies depending on the conditions of the river bed, on which the barrier body 1s to be erected. When the river bed is substantially horizontal, the angle (9) is preferable to be 45. By making the angle of inclination 45, the effect of the water weight of keeping down the barrier body can be expected. If the river bed is inclined, the angle is to be made greater. For instance, the river bed is inclined at least at an angle of 10, the angle between the upper stream surface of the barrier body and the river bed is made 55.

However, if the angle of inclination of the barrier body is too large, it will be difiicult to satisfy the safety conditions. Therefore, the angle of inclination is practically between 35 to 55.

The point (0) in FIG. 6, where each staying member 4 is connected to each longitudinal rod 6 is preferable to be 60 to of the height (H) of the barrier body from the lower end thereof, wherein the height of the barrier body designates the vertical distance from the top of the staying members to the longitudinal rods 6 at a right angle will be advantageous in the point that the shearing force is not working on the connected surface, but is not desirable because it sacrifices the stability of the construction. Therefore, the point (0) should be higher than the point where the longitudinal rods and the staying members would be connected with each other at a right angle. The most desirable is the point where Ma and M0 in the bending moment of the longitudinal rod 6 are the same as shown in FIG. 7. However, from the view point of securing the balanced form of the whole barrier body and improving the rigidity of the top part of the barrier body the theoretically most desirable point (0) is that which corresponds to H/ /'2 However, practically it may be 60 to 100% of the height of the barrier body from the bottom thereof as above mentioned. For instance, by applying the reinforcements 15 and 15 it is possible to set the point (0) to a sufficient high position, or the delta form may be permitted. Further, according to the conditions of the river, it is also possible to set the point at (O) at 60% of the height of the barrier body.

The lower end part of the staying member 4 is preferable to be laid more on upper stream side than the foot of a perpendicular fallen from the top part of the barrier body 1 in order to prevent the staying members 4 from being directly stuck by falling debris running over the barrier body in the flood time. This is, however, not an indispensable condition of this invention, because a stream does not fall down perpendicularly from the top of the barrier body but somewhat to the down stream side. Further, it is also desirable to lay the lower part of each staying member 4 at the upper stream side, possibly away from the falling point of sand and gravel in order to protect the staying member from sustaining direct or indirect damages due to washing away or impact given by them.

Thus, the construction of the buttress type steel darn as a debris barrier is very simple. That is, only by assembling steel materials ready made in a factory, that is, by connecting staying members, the lower ends of said staying members being fixed to a foundation established on the river bed, to a steel barrier body, said barrier body being prepared by connecting screenwise lateral rods to longitudinal rods and being fixed at its lower end to a foundation established on the river bed in such an inclined state that the upper part of the barrier body is positioned more to the down stream side than the lower part thereof, a debris barrier having a great durability and stability against the water pressure and debris pressure acting on the barrier body surface can be obtained on a spot on the bed of a river having swift stream very rapidly and economically with materials of smaller quantities.

Having thus described the invention, what is claimed 1. A buttress type steel frame darn as a debris barrier adapted to be established on a steep bed of a river in mountainous region which river is susceptible of rapidly rising in the stream bed containing a lot of debris during flood time, said debris barrier body comprising in combination:

(a) a plurality of longitudinal rods (6) fixed to a first foundation (3) established in the river bed,

spreading in laterally spaced apart relation completely across the river from one side to another side of river banks, in such an inclined state that the upper part of the barrier body is positioned more to the down stream side than the lower part thereof,

(b) a like plurality of reversely inclined staying members (4), each of which being fixed at its root to a second foundation (5) established downstream of said first-mentioned foundation on the river bed and being connected at its top to a position upwardly of the middle part of each of said longitudinal rods; and

(c) debris screening means overlaying said longitudinal rods, said screening means including a plurality of vertically spaced lateral rods (7) fixed to said longitudinal rods (6) in front of the latter screenwise in such a way that gaps (8) of relatively small distance are formed between said rods, whereby large debris is prevented being swept away by the current while limited amounts of water, fine sand and earth may pass therethrough.

2 The debris barrier claimed in claim 1 in which an angle of the barrier body to the river bed is made within the range of from 35 to and preferably at approximately 45.

3. The debris barrier claimed in claim 1, in which each staying member is connected to the barrier body at a position corresponding to to of the vertical height of the barrier body from the lower end of the latter.

4. The debris barrier claimed in claim 1 in which the barrier is formed with a generally concave upper surface wherein the upper ends of several of the longitudinal rods disposed centrally of the river are foreshortened at their upper ends relative to those disposed on opposite shore side areas of said barrier, and the lateral rods (7 fixed to said longitudinal rods (6) do not span the area of said foreshortened longitudinal rods (6), thereby defining a central channel area through which to direct swiftly rising surging flood waters of the associated river or stream.

References Cited UNITED STATES PATENTS 964,362 7/1910 Airhart 613 1,858,976 5/1932 Thornley 613 2,055,150 9/1936 Heskett 6l-3 2,068,537 1/1937 Dorn 6l3 EARL J. WITMER, Primary Examiner 

